Structure and Function of the Skin Flashcards
What structures are found of the epidermis of the skin?
avascular epithelium which undergoes proliferation and synthesises keratin
Components of the dermis
blood vessels, lymphatics, cutaneous nerves
collagen and elastic present but not replaced with age
Components of the hypodermis
blood vessels, nerves, lymphatics
adipose tissue
skin ligaments
What happens when the skin is burned?
There is a loss of the skin barrier function which can result in dangerous fluid loss and infection
What type of epithelium is found at the epidermis?
Stratified squamous keratinised epithelium
What is the deepest layer of the epidermis?
Stratum basale
What is the function of hemidesmosomes in the stratum basale?
Anchors basal cells to basal lamina
What attaches the dermis to the basal lamina of stratum basale?
Collagen VII
What is the medical term for blistering?
Dystrophic epidermolysis bullosa
What changes during blistering?
Collagen VII is mutated
What is found at the stratum spinosum?
Intermediate filaments K1/K10 expressed
Desmosomes link cell to cell
Hemidesmosomes which link basal cells with basement membrane
What regulates keratin in skin?
Differentiation programme regulates keratin expression pattern
Where is filaggrin found?
Keratohyaline granules in S.granulosum
Uses of filaggrin and its precursor profilaggrin
Maintain optimal skin barrier
Aids keratin filament aggregation
Inhibits water loss
What can mutations of filaggrin cause?
keratinisation disorders
eczema
null mutations associated with asthma
Where are melanocytes found?
Basal layer of epidermis
What is the function of melanocytes?
Release brown pigment melanin
What does melanin do?
Absorbs UV-B and prevents DNA damage to underlying cells of hypodermis
What is melanoma?
Tumor of melanocytes caused by exposure to UV radiation
Where are melanocytes derived from?
neural crest cells that originate near the developing nervous system and spread into the embryo
How are melanosomes developed and transferred to keratinocytes?
Melanosomes are specialised lysosomes which are synthesised in melanocytes and undergo exocytosis to be transferred to keratinocytes
Where are Langerhan cells derived from?
Monocytes
Where are most Langerhan cells found?
Stratum spinosum
What is the antigen processing function of Langerhan cells?
Langerhan cells activated in skin, migrate to lymph nodes, capture, process and present antigens
Explain virus degradation
Langerhan cells express Langerin which help degrade viruses in specialised endosomes called Birbeck granules
Where is the dermo-epidermal junction and what is its function?
Found in the dermis and is complex to prevent shearing. Papillae flatten with age
Where is the papillary dermis found and what is it comprised of?
Found superficial to the reticular dermis comprised of fine collagen fibres, elastic fibres, small blood vessels and nerves
What does the hypodermis support?
Deepest part of hair follicles
Eccrine/merocine and apocrine sweat glands
Site of vitamin D production
Composition of eccrine sweat glands
Simple coiled and tubular, secrete a watery fluid. Found in dermis and superficial fascia but ducts open onto the surface of the skin
What controls eccrine sweat glands?
Sympathetic nervous system- important in thermoregulation and as a response to fear
Properties of apocrine sweat glands?
Open into hair follicles in axillary and genital region and secrete milky fluid containing pheromones
Where does the hair shaft grow from and what is it composed of?
Grows from the hair bulb and is composed of keratin, associated with sebaceous glands that open into the follicle and secrete sebum
Describe how goose bumps are produced?
Arrector pili contracts smooth muscle attached to the papillary dermis and the sheath of the follicle which pulls the hair upright- controlled by sympathetic NS
What forms a pilosebaceous unit?
hair follicle, sebaceous gland, hair shaft and arrector pilli
What are mammary glands?
modified apocrine sweat glands, lactation under hormonal control
Properties of nails
Nail plate formed from keratin
Growth from nail root which passes deep into the dermis
Properties of teeth
Enamel develops from epithelium
dentine, pulp and periodontal membrane is mesodermal
What is the periodontal membrane?
Fibrous joint between teeth and skull
What are pain receptors?
Free nerve endings
Nociceptors which responds when tissues are being damaged or close to being damaged
Temperature receptors?
Free nerve endings
Separate receptors for cold and heat
Touch organs?
Meissner’s corpuscles- beneath the epidermis
Merkel cells for light touch- stratum basale
Pressure organ?
Pacinian corpuscles - dermis
Vibration organ?
Meissner’s and Pacinian corpuscles- dermis
What comprises the reticular epidermis?
Coarser collagen and elastic fibres and larger blood vessels and nerves
What are the layers of the epidermis from top to bottom?
S. corneum S. Lucidum S. Granulosum S. Spinosum S. Basale
